Fabricating semiconductor devices such as logic and memory devices typically includes processing a substrate such as a semiconductor wafer using a large number of semiconductor fabrication processes to form various features and multiple levels of the semiconductor devices. Examples of semiconductor fabrication processes include, but are not limited to, lithography, chemical-mechanical polishing, etch, deposition, and ion implantation. Multiple semiconductor devices may be fabricated in an arrangement on a single semiconductor wafer and then separated into individual semiconductor devices.
As the dimensions of semiconductor devices decrease, the demand for improved inspection processes and tools increases. Inspection processes are used at various steps during a semiconductor manufacturing process to detect defects on wafers, leading to increased device yield. Many different types of inspection tools have been developed for the inspection of semiconductor wafers. Defect inspection is currently performed using techniques such as bright field (BF) imaging, dark field (DF) imaging, and scattering. The type of inspection tool that is used for inspecting semiconductor wafers may be selected based on, for example, characteristics of the defects of interest and characteristics of the wafers that will be inspected. For example, some inspection tools are designed to inspect unpatterned semiconductor wafers or patterned semiconductor wafers.
Patterned wafer inspection is of particular interest and importance to the semiconductor industry because processed semiconductor wafers usually have a pattern of features formed thereon. Inspection of patterned wafers is, therefore, important to accurately detect defects that may have been formed on the wafer during, or as a result of, processing.
Many inspection tools have been developed for patterned wafer inspection. For example, patterned wafer inspection tools commonly utilize spatial filters to enhance patterned wafer inspection. These spatial filters may include, but are not limited to, Fourier filters and apodizing filters.
Since the light scattered from patterned features depends on various characteristics of the patterned features such as lateral dimension and period, the design of the spatial filter also depends on such characteristics of the patterned features. As a result, the spatial filter must be designed based on known or determined characteristics of the patterned features and must vary as different patterned features are being inspected. Therefore, it is desirable to provide a system and method that cures the defects of the prior art.